Distributing system



Dec, 2, 1924.

H. PEARCE DISTHIBUTING SYSTEM rlled May 22, 1920 6 Sheets-Sheet l lNvENToR Herbert pea/ce ATTRNEY Dec. 2, y H. PEARCE DISTRIBUTING SYSTEM flied May 22, 1920 6 Sheets-Sheet 2 f Y/f4 f5 '6 E 3 I6 J J 2\ *24 L L L 70 3:/ i /2 /4 9 )f E0 2] 22 f2; 73 l "l V l I v? lla (/9 i @s 91 3 Z Q .4, 4, L 6

z y f6 [5 2.5/ 24: 26 I J Z5 L L 1 c 74 ff l'/ /7 f@ f9 a* 2! Q22 7gg/ 1 r ll' .9 WITNESSES: INVENTOR /0 54 /a f m mi /L/eref ,Dea ce.

.u o un HN" ATT RNY Dec. 2, 1924. 1,517,247

H. PEARCE DISTRIBUTING SYSTEM r'lled May 22, 1920 6 Sheets-Sheet 5 VVV l [AAAI- F mvENToRl y #erbeff Pearce.

ZTTRNEY H. PEARCE DI STRIBUTING SYSTEM 6 Sheets-Sheet 4 rlled May 22 1.920

/Q/[ i!!! L l J 52 15 14 y l 1 1 WITNEssEs: \36 INVENTOR /@'Mannw Ej I0 Herbert Pearce ATTORNEY e sheets-sheet s H. PEARCE Filed May 22 DISTRIBUTNG SYSTEM INVENTOR Hefefearce.

TTORNEY lllnlllaln ill.. villain-ul- SSES:

H. PEARCE DISTRIBUTINQ SYSTEM :flied Ma`y 22,

1920 6 Sheets-Sheet 6 RNVENTOR la fie/"bari Pearce WITNESSES: Qfi

ATTORNEY Patented Dec. 2, 1924.

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To all wlwm it ma Bev lit A known t at L, Hmm Panca, 'a subiect'l of the King of GreatBritain, and

a resident `of Stretford.. in the county o'f-- l Lancaster, England, have invented a new and useful Improvement in Distributirg Systems, of which the following is a speci cation. f

My 'n'vention relates yto protective gear l0 for alternating electric current systems and particularly `to apparatus of this kind desi to protect a system not only when faults arise but, also, on they occasion of'a 1 fault to ground of rone or more lof the con- 15 ductors.

system of protection for an electric distribvuting system comprising means that may be adjusted to operatef at a relatively large `20 value `of current `toprotect -the 4system against excessivey currents arising from short circuit or unbalance conditions and -means vthat ma beadju'sted to operate'at a vrelatively smal value of current to protect v the system from aggravation of ground conditions. e r l AAnother'object of my invention is to rovde -a system of the almveindicated c aracter that may be applied toprotect analae lel-connected-feeder circuits o'r trans ating apparatus, 'such as dynamo-electric machines vor transformers.

In apparatus of this kind, as is well known, relayfdevices are commonly emal' ployed that ane connected Awith the secondaries of series transformers inthe various conductors ofthe system, said relays` controlling the `operation ,off'crcuit breakers for `cuttingout a conductor or piece o fap# aratus, such as a transformer or generator,

m the system when necessity arises. Man

arrangements have been devised in whic the same relayslare utilized for protecting the system 4 6 ductors and n rangements the fact that the use of aisensitive relay is aga-inst faults between confaults to ground. Such arnot always permissible in'dealing with faults between conductors .as it is liable to be actuon (the occasion-Tof an overload and j be 'describedwith reference to the accom- One object of myinvention is-to provide a operation of the protective system em tr'atingthe application thereto of the pro- `rangement is applied to both Vends of may 'cause inconvenience due -toswitched into circuit before another conductor. On the other hand, in order to protect the system in case of earth leakage, the relay shouldlbe as 'sensitive as possible.

In view `of the above conditions and in order to "avoid the disadvantages referred to, I provide, in addition to relays that protect against' faults between` conductors,` a relay thatma bemore sensitive andthat operates only lnthe event of a fault arising .which involves leakage to earth.

`In orderthat the nature of the invention may be more clearly understood, it will now panying drawings which are diagrammatic views of `various -systems embodying my invention; n y A e Figures `1, 2, 3 and 4 are diagrammatic views of electrical circuits illustratin the ing my inventionnpon the occurrence gf faults of differenti-types at different points in the system; s Y

Fig. 5 is a schematic view of "a relay embodying my invention that maybe employed 'in theprotective systemdisclosed herein' Fig.6 is la diagrammatic view Aof an elec `trcal circuit,l illustrating the connection of the-operating coils of the relayin Fig.;5 to the systemsillustra'ted in Figs; 1 tod, i114;` elusive; v i f l Figs.`7, 8 and 9 are diagrammatic views 'of single-phase and two-phase circuits, illustective system embodying my invention;

Fig.l 10 isa diagrammatic view of an electrical clrcuitin whichthe protectivesystem. is applied to protect the windings of a dynamo `electric machine; n I

Fig. 11 is a diagrammatic viewof an `electrical system in which fthe' protective ral. lel-connected-transmission' circuits, an

Fig. `12 is a diagrammatic view of an electrical. circuit, illustrating the application o f my protective system thereto.

`Figure ,1 is a diagrammatic viewof a three-'phase system having two sets of feeder conductors 1, 2, 8 and 4, 5,6 in parallel 100 relation for connecting av supply circuit 7 to a set of bus-bar conductors 8 or other circuit in which energy is to be utilized. Series transformers with ysecondary windings 9, 10, 11 and 12, 13, 14 are provided near each end of both sets of the feeder conductors, one terminal of tlie three secondary windings of the transformers in each set of feeder conductors being connected together at 15 and 16 to form a neutral point. The other terminal of each of the secondar windin 9, 10, 11 is respectively connected to ther/f e terminals of the secondaries 12, 13, 14 of the conductor of the corresponding phase in the second set of feeder con- -ductors and the connecting conductors 17 18, 19 are each joined to one terminal of the relays 20, 21, 22. There are thus three relays, one corresponding to the conductor of each phase. lThe free terminals of the relays 20, 21, 22 are joined together at 23 and connected through a fourth relay 24 to the two neutral points 15, 16 of the six secondary windings 9, 10, 11, 12 13, 14 b the conductors 25, 26. The secondar win ings corresponding to the two fee er conductors of any one phase are so connected that the relays 20. 21, 22 will be traversed by currents kof a value depending upon the difference between the currents traversin -rthe respective secondary windin s 9 and 1 10 and 13, 11 and 14, to which t ey areyconnected.

Fig. 2 illustrates the course of the currents (shown b the arrows) inthe relay circuits, set up h an earth fault at X, for example, externa to the feeder circuits 1, 2, 3 and 4, 5, 6 and approximately equi-distant from the two sets of transformer windings 9, 10, 11 and 12, 13, 14,so that the latter are traversed by equal earth currents. The

l current will traverse the path 9, 17, 12, 26,

% and'no current will traverse any of the relays. refer only to that portion of the current that lis set up by the leakage current andv that the load currents are not indicated. Y

If the fault were so located that unequal l currents would flow in the secondary windings' of the transformers, ya current would flow through the relay 24 as well as throu h one or' more of the relays 20, 2l, 22. or example, Fig. 3 illustrates the course of the currents in the case of an earth fault on the phase conductor 4 at Y.. As regards the equipment which is located at the substation end of a air of parallel feeder conductors, it wil be seen from the drawing that, in this case, the current reverses in the secondary winding 12 and traverses both the relays 20 and 24.

Fig. 4 shows the path traversed by the currents in the case of a fault between two phases 1 and 2 of the feeder conductors when no leakage to earth is involved, as

It is understood that 'the arrowsv shown by the dotted line Z, for example. In this case, the current traverses the winding 9, therelays 2O and 21, and the winding 10, and similarly the winding 12, the relays 20 and 21, and the winding 13, but no current traverses the relay 24.

It will be seen from the above whereas currents traverse one or more of the relays 20, 21, 22, when unbalancing occurs due to any kind of fault, current will only traverse the relay 24 when an unbalanced fault to earth occurs as shown, for example, in Fig. 3. Consequently, the relays 20, 21, 22 can be so made or ad'usted with coarse setting that they will on y operate when the out-ofbalance current flowing in the feeder conductors is greater than a predetermined amount which may be, for example, the normal current flowing in the feeder conductor when it is fully loaded. By this means, operation of the relays is'avoided, in case one feeder conductor is switched into circuit before the other. The relay 24, however, may be made very sensitivel as it is not operated b 'the out-of-balance current that is effected y faults between conductors, but only when an earth leaka occurs.

It will be clear fromV what ligas been said above that no difiiculty is experienced when only one -of the two feeder conductors is connected into circuit, and in such cases the feeder conductor is provided with simple overload protection by means of the three relays 20, 21 and 22 and simple leakage protection by the fourth rela 24. The overload relays 20, 21, 22 may provided with a time limit device so constructed that the delay might be to zero when the relays rform their normal function of protectin against faults between hases when bot feeder conductors are in circuit, or, a time delay device may be provided 'when it is necessary to operate for any length of time with a single feeder conductor connected. The latter condition, however, is a special one and, in normal operation, the time delay would not be re- .quired even when the feeder conductors were being switched into, and out of, circuit.

As the fourth, orfleaka vrelay 24 protects the system against aults to ground, it will be clear that one of the three first mentioned or overload relays 20, 21', 22 may be omitted, without inconvenience, if desired.

The series transformersl cannot, as is well known, be so constructed that-the will vbe balanced at all conditions of loa l, that is to say, they may-balance closely when normal currents traverse their respective conductors and ma be considerably out-ofbalance when a s ort-circuit current obtains. If necessary, resistances or` reactances may be provided in lei-ies with any transformers. i

to attract a rela transformer, rconductor or relay, the balance -under short-circuit conditions, but it ispreferable, however, to vconstruct the relays with `biasing coils that arecon- 'nected rin the secondary windings ofthe With a threep three biasing `windin'gsxon each relay, thus forming a polyphase restraining magnet produces much less vibrationr and chattering of the 'relay' amature than is set up by sin le-liase iasing coils such as have previous yV en used for this purpose. A referred construction of Asuch a relay is ilustrated in Fig..5. An operating coil 27 is wound on a magnet 28'that is arranged y armature 29.' which vis partially balance b a oounterweight 30, and ,is provided wit `an auxiliary armature 31, at right angles to the first, that'is attracted by ,the three-phase magnet 32 which is rovide'd with plurality of: coils 33, 34, 35. hese coils mayjbeso connected in the secondary circuits of` the yrespective transformers, as shown `in Figy, that they may betraversedby currents .proportional to the load currents. n The leakage relay ma therefore, be `rovided with a restraint or ias that depen s upon the'current'that traverses the feeder conductors. The relay may thus ybevery sensitive to earth leakage currents, at normal load, but will have its sensitiveness reduced when the feederconductors aretraversed by short-circuit prove suilicient to provide restraining coi s on the relays that are/connected yto two ofthe phases only.

'A relay constructed in this manner may be `used on single feeders in which case the four relays 'will -be .connected incircuit withthe secondarie's of three transr formers-only. 4 n

Fi 7 shows how v,the invention may be applled to a single-phase system having two sets of feeder-conductors connected in parallel relation. `At each' end ofthe feeder conductors,four series transformers are provided with vtheir secondary windings'i), 10k,

and12, 13, connected in a closed tcircuitand equi-potential points of this circuit are connected, in Aa well-known manner, through a vrelay 20 corresponding-'to kthe overload relays hereinbefore mentioned.

mon termimls of the secondary windings 9 10 and 12, 13 `that are also equi-potential points, under normal conditions, (are connected together by the .conductor 25, 26, that is connected to one of the first-mentioned vequipotential points through another relay `24. This relay corresponds to the leakage relay 24.shown in Figs. 1 to 4." The restraining y or biasinggm l lay, that is in series with the transformer secondary windings, will be a single-phat toimprove hase there may be v14", respectively, with such protectivev systems in order `the earth leakage relay The corn-,-

above,

4,applied ,to ythe' agnet 38 ofthe]y rema et although it may be prviad with tinlg device, t t

n Fig. 8, the invention is shown asaplied to a two-phase four-wire system of istribution. This ynecessitates the addition secondary windings are indicated at 11' and coil 35 included inthe circuit and a sec- 0nd overload relay22.

Fig. 9 shows the invention as ap'plxied to a two-phase three-wire system. ef arrangements in this case are similar to those shown in Fig. l but the ratio of thetransformers in the common phasey conductors of each feeder conductor must be proportioned to suit the additional current that traverses these conductors. The operation of the arrangements shown in` Figs..8 and 9 will be readily understood, b those skilled inthe art, without further escription, as it is substantially the same as al y described with reference to Figs. 1 to 4 of the drawings. v

The em loyment of an dealing Vwith earth leaka described, may be applic extra relay 'for e, as hereinabove to the protection .of transformers in which `a set of series transformers, that are connected on the primary side? of the 'transformer that is to be protected, have their secondary windings balanced against -'r'xorrespmiding `secondary V'windings of aset of series transformers that are connected on the secondarysidevofv the ltransformerthat is to be protected. Heretofore, it has been usual in to employ relays a coarse setting. or a considerable mit, or both of hese characteristics that the relays might erated' by the out-of-balance current ythat obtained when lone side of the-transformer was switched 'into circuit before the kother' side W ith the usual arrangement the relayshave the same setting for earth leakage faults as they have'for faults between conductors, which, as before mentioned, is undesirable. f If the construction of rela ing coils, as herein `indicat having time 1 sfwith biassensitive'and theoverload relays less sensitive to obtain the advantages pointed out ythe arrangement is shown 'as I rotectionI of a three-phase generator'in which an earthng' resistance is In Figlj 1e,l

ynmctll t0 the neutral pointvv 36`ofthe systems. The 'generator windi n37, v 88,439 are connected through a'circuit interrupter 40 to the busbarey 41'. Y Series transformen yare rprovided .-inffthe' phase conductors betweenigtheggenerator terinnalsf 88, and the 41, 'and phase conditi-.tors

a second restraining l of transformers for the fourth wire. -The i.

los f not .be 0P- f' 11a l is adopted, may be made very between the generator windings 37, 38, 39 and the neutral point 36, the secondary windings of the transformers 9, 10, 11, 12, 13, 14 being connected with overload relays 21 and 22 and a leakage relay 24. The operationof this arrangement of relays is simllar to that of the arrangement shown in Fig. 1 and 'will be understood without further description. y

The following advantages are obtained, namely: The protection against earth faults is more sensitive` than with the usual arrangement of relays; a smaller earthing resistance is re uired; and the transformers that are emp oyed in the protective gear need not be constructed to balance so accurately. In addition to these advantages a greater `portion of the generator winding may be rotected. This will` be clear from the fol owing considerations. If an earthing resistor that is connected ,to the neutral oint of a three-phase generator is designedp to permit the traversal of a current of predetermined value when one phasev terminal is connected to earth, only half that current will flow' if the mid-pointof a phase winding is connected to earth, and similarly for other portions of the winding, the maximum earth current which may flow at normal voltage depends upon the particular portion of the winding that is earthed. Consequently, .if a relay operates at a value corresponding to fifty per cent ofthe maximum current that may `traverse the earthing resistance, then only half of the generator winding willbe protected, but

if the relay is madev suciently sensitive, as it can be with the arrangement shown, to operate at a value corresponding to five per cent of ninety-five per cent of the winding is protectedagainst earth faults;

In the arrangement shown in Fig. 1 where the invention is applied to the protection of one end of a pair of parallel feeders, in the event of afault yoccurringon either feeder, both feeders willbe cut outy of circuit and the supply may thus be entirely interrupted. In order to-avoid this occurrence, the fourth relay 24, hereinbefore termed the leakage relay, may advantageouslytake the form of the well known wattmeter type of relay. As shown in Fig. 11, the current coil 24 of the relay is connected in circuit with the secondary windings 9, 10, 11 and v12, 13, 14 ofthe protective transformers, and the potential coil 42 is connected betweenground and the star, or neutral, point of any convenient generator, transformer or similar apparatus. In the upper part of. Fig. 11, 4for example, that i's, in the arrangement applied at the generator end of the feeders, the potential coil 42 is shown connected to the secondary winding 43 of av potential transformer, the primary winding 44 of the maximum current, .then

point of astar wound transformer or reactance 48 connected to the substation busbars 49.

In operation, if an earth occurs on the third phase 6 of the second feeder, the transformer winding 14 will be traversed by a current of greater value than transformer 11 and a current ofk a value that is the difference between the values of these currents will traverse the relay winding 24. At the same time, the traversal of leakage current to ground creates a potential across the resistance 45 that induces a potential in the secondary winding 43 of the potential transformer `and thus energizes the potential winding 42 of the leakage relay 24.

The primary leakage current is set up by the third phase of the generator, and for the purpose of this invention this phase winding may be regarded as a single-phase generator producing a current equal to the leakage current at a'vo'ltage equal to the potential drop across the resistance 45. This current and potential will be more or less of the same phase accordingto the relative amount of resistance and reactance which the current must traverse. v Consequently, a wattmeter relay provided with a current winding 24 and a potential winding 42 may be so provided with two sets of contacts that if the current in the 11 the second respondingly, 11 1s greater than the current in the windin 14, the interrupter in the first feeder wil be opened.

With the arrangement in Fig. 11, the phase relays 21 and 22 are required to operate both interrupters simultaneous] whereas the,wattmete`r` relay is require to open either the one switch or the other according to which is the faulty circuit. This is arranged by 4fitting each oil switch with two trip coils. one for use with the phase relays 21 and 22 and one foruse with the wattmeter leakage relay 24. Alternatively, the

lsame result could be obtainedby duplicating the relays instead ofthe trip'coils.A

The potential transformer 43, 44'or 43, 47 is employedin order to reduce the voltage on the potential coil of the wattmeter relay to a safe value. If the relays are situated in a power house where an earthing resistor is provided, the potential transformer may conveniently be connected autom the terminals of such resistor.

v winding 14 is greater l than that in the winding feeder interrupter will be opened, and, corif the current in the winding' `iai'y circuitv for connectin corres describedv with reference to the ordinary relays.

In Fig.`12, the invention is shown as applied to the protection of a single feeder circuit. In this case the overload relays 20, 21, 22 at the two ends of the feeder to be protected arerespectively connected in series y pilot wires 50, 51, 52 and the secondary windings 9, y10, 11, and 12, 13, 14 of the series transformers of each phase are also res ectively connected in series to op ose eac other under normal conditions. he restraining or biasing windings33, 34, 35 at each end of the feeder are connected between the respective pilotvk wires and the neutral int 'of the secondary circuits through the eakage rela s 24 andthe high voltages that are induce across the protective transformers when the feeder conductors are traversedby heavy short-circuit currents are utilized tc energize the restraining windings 33, 34, 35 so that very sensitive leakage relays may be employed.

I do not limit my invention to the specific arrangements illustrated, as various modifications may be made therein within the spirit and sco e of the invention as set forth in the appen ed claims.

I claim as my invention:

1. In an electric distributing system, the combination with a translating apparatus, of means responsive to the current traversing the windings of the translating apparatus at one end thereof and responsive to the currentxtraversing the windings at the other end of the paratus, electro-responsive means adjust to operate when a relatively large. value of current entirely traverses the apparatus, and meansadjusted to operate when a relatively small value lof currentv traverses a portion of thev windings of the apparatus.

2. A protective system for a polyphase translating apparatus provided with. a plurality of windings, comprising current transformers disposed at the terminals of the windings, auxiliary ,circuitconductors connecting corresponding transformers and electro-responsive devices connected tween the auxiliary, conductors, one of said devices being adjusted to operate when a relatively lar e value of current traverses the correspon ing winding of the' apparatus and another of said devices bein adjusted to operate when a relatively sma l value of current traverses a portion of' a winding of the apparatus. c y j 3. n a. power-distribution s stem, the combination with two sets of con uctors and current transformers therefor, of an auxilriding current transformers an norma y decuit with the auxiliary circuits 1 and conductor.

bearing predetermined ratios,

energized means connected across saidauxiliary circuit to be ener 'zed upon the occurrence of abnormal conditions in either set of conductors, one of such means being adjusted to operate at a relatively low value of current caused to traverse a conductor by reason of a ground thereon.

4. In combination, a source of energy comprising a plurality of windings, two sets of conductors ,f connected thereto, current transformers for the respective setsof conductors, auxiliary circuit conductors for connecting corresponding current -transformers of both sets of conductors, means connected between the vauxiliary conductors to respond to currents resulting from predetermined faults on a conductor of one set, and means associated with the former means to res ond to a current resulting from a roun on a conductor of one set of conuctors or on one of the windings.

5. The combination with a polyphase a paratusprovided with a plurality of Wintriings, the neutral point of which is grounded, of a plurality of current transformers connecte between the neutral point and one set of terminals of the windings and a pluralit of transformersbetween the other termina s of the windings and an` external circuit, auxiliaryA conductors for connectin corresponding transformers in circuit an means operatively connected in circuit with such auxiliary conductors to indicate the occurrence of a ground upon a winding of the apparatus and upon the occurrence of any fault on the conductors beyond the terminals of the windings.

, `6. The combination with two sets of con? ductorsadaptedto'be traversed by currents bearing predetermined ratios7 of current transformers in circuit therewith, auxiliary circuits connecting the transformers and electro-responsive means connected in ciro n erative u on the occurrence ofl both fau to groun andfaults between conductors. g

7. The combination with two sets of lcon.-` ductors adapted to be traversed by currentsl of current I bearing predetermined rratios transformers in circuit therewith, auxiliary circuits connecting the transformersand electro-responsive means connected infcir'- cuit- `with the auxiliary circuits comprising means responsive to a variation from the predetermined ratios of the Acurrent and means yresponsive to a 8. The combnationwith two seta of conductors adapted' to be' traversed by currents of current tr'ansformersin circuit therewith', auxilia circuitsl connecting ythe transformers an electro-responsive means connected in circuit with the auxiliary circuits y v com rising means `adjusted-to operate at a relltively iio ground fault on a v large value of current in response to an abnormal variation from the ratio to be pre served between the currents traversing the two sets of conductors and means adjusted to operate at a relatively small value of ground current.

9. The combination with a dynamo-electric machine provided with a plurality of windings, of current transformers disposed between the terminals of the windings and external conductors to be connected to the windings, auxiliary conductors for connecting the transformers in' circuit, means adjusted to operate upon the occurrence of redetermined conditions normally manilested by currents of excessive value and mea-ns 'adjusted to operate upon the occurrence of predetermined conditions normall manifested by currents of relatively smal value.

10. In combination, an alternating-current circuit, current transformers disposed at predetermined positions thereof, connecting conductors between the transformers,

and a relay connected to the conductors and comprising means actuated when a ground current traverses they circuit if not more than normal circuit current traverses the circuit.

11. In an electric circuit, the combination with a plurality of current transformers and' connecting conductors therefor, of means responsive to a ground current, and means for controlling the responsiveness narran thereof in accordance with the value of the circuit current.

12. In combination, an alternating-current circuit, current transformers at each end thereof, relays associated with the current transformers, means for connecting the relays in circuit with the transformers, means ener ized upon the occurrence of a ground on t ecircuit to be actuated to perorm a predetermined operation and means for controlling such actuation in accordance with the degree of balance between the currents traversin both ends of the circuit. 13. The com ination with an alternating current electrical circuit, of a protective device therefor comprising a plurality of starconnected current transformer groups associated with at least two points msaid electrical circuit, the neutral oints of said transformer groups being e ectrically connected, other terminals of co-operating transformers in each of said oups being electricaly connected, a plura ity of starconnecte relays respectively in circuit with the said transformers and a ground relay in circuit with the neutral point of said relay connection and the neutral point of said transformer groups.

In testimony whereof, I yhave hereunto subscribed my name this first day of May, 1920.

HERBERT PEAIRCE. 

